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Operators

An operator, in a programming language, is a tool used to modify, manipulate, or work with individual values or variables. It is almost always represented using some form of word or symbol, but it differs from a function in that it is simply put before, after, or between values or variables.

Modern programming languages have MANY operators. We will define the most important ones below - a lot of them will seem obvious, but having the reference could be valuable.

I have bolded the ones that might have something kind of surprising or that you might not have seen before - if you only read a few of them, read those!

Operators on Numeric Values

Arithmetic Operators

The operators you are most familar with: these do math.

The examples below represent the results from TypeScript. java would be mostly the same. The exception shown below is integer division, which only exists on typescript.

Operator	Code Sample	Result	IB
Addition (`+`)	`let a = 2; let b = 7;` `a + b`	`9`
Subtraction (`-`)	`a - b`	`-5`	`+`
Multiplication (`*`)	`a * b`	`14`	`*`
Division (`/`)	`a / b` `b / a`	`0.2857142857142857` `3.5`	`/`
Modulus or Remainder (`%`)	`a % b` `b % a`	`2` (remainder of 2 / 7) `1` (remainder of 7 / 2)	`mod`
Integer Division (`/`) (java only)	`int a = 2, b = 7`; `a / b` `b / a`	`0` `3`	`div`
Exponentiation (``)** (TypeScipt only)	`a ** b`	`128` (2⁷)	N/A

Comparison Operators

These operators return boolean values - either true or false.

Operator	Code Sample	Result	IB
Greater than (`>`)	`2 > 3` `3 > 3` `4 > 3`	`false` `false` `true`	`>`
Greater than or equal (`>=`)	`2 >= 3` `3 >= 3` `4 >= 3`	`false` `true` `true`	`≥`
Less than (`<`)	`2 < 3` `3 < 3` `4 < 3`	`true` `false` `false`	`<`
Less than or equal (`<=`)	`2 <= 3` `3 <= 3` `4 <= 3`	`true` `true` `false`	`≤`
Equal to (`==`)	`2 == 3` `3 == 3` `4 == 3`	`false` `true` `false`	`=`
Not Equal (`!=`)	`2 != 3` `3 != 3` `4 != 3`	`true` `false` `true`	`≠`

Operators on Strings

Operator	Code Sample	Result	IB
Concatenation (`+`)	`let b = "bob"`; `b + " " + b + "mary";`	bob bobmary	N/A

Note that since the same operator, + is used for strings and numbers, you can get some odd results if you aren’t careful. Feel free to use ts-node in your command line to test these results below.

"a" + 3; // result: "a3" - converts 3 to a string then concatentes
3 + "a"; // result: "3a" - same as above
3 + 2 + "a" // result: "5a" - does 3 + 2 first, then concatenates with a
3 + (2 + "a") // result: 32a. Concatenates 2 and a to "2a" then concatenates the 3.
"a" + 3 + 2 // result: a32
"a" + (3 + 2) // result: a5
"a" + (3 - 2) // result: a1
"a" + 3 - 2 // error! tries to do "a3" - 2, which is not possible.

Logic Operators

These are used when working with boolean statements, to combine multiple statments together or change them around. You will commonly see them in if statements.

Operator	Code Sample	Result	IB
And (`&&`) True only if both sides are true	`(3 > 2) && (2 > 1)` `(3 > 2) && (2 == 3)`	`true` `false`	`AND`
Or (`\|\|`) True if EITHER or BOTH sides are true	`(3 > 2) \|\| (2 > 1)` `(3 > 2) \|\| (2 == 3)`	`true` `true`	`OR`
Not (`!`) Comes BEFORE a boolean statement, and changes it from `true` to `false` or vice versa.	`!(3 > 2)` `!(2 == 3)`	`false` `true`	`NOT`

Assignment Operators

These operators change the value stored inside a variable. By far the most important one is the first one; we will mostly avoid using the others, but they exist.

Operator	Code	Result	Note	IB
Assignment (`=`)	`a = 3;` `a = a + 1;`	`a` has value 3 now `a` has value 4		`=`
Increment (`++`) increases variable value by 1. Used AFTER the variable.	`a = 3;` `a++;`	`a` has value 3 now `a` has value 4	equivalent to `a = a + 1`	N/A
Decrement (`--`) decreases variable value by 1. Used AFTER the variable.	`a = 3;` `a--;`	`a` has value 3 now `a` has value 2	equivalent to `a = a - 1`	N/A
Addition assignment (`+=`) increases variable on left by amount on right.	`a = 3;` `a += 4;`	`a` has value 3 now `a` has value 7	equivalent to `a = a + 4`	N/A

There are also versions of the last one for subtraction -=, division /=, and multiplication *=. You should not use ANY of these, generally, as they can be hard to read since they look too much like ==. The ++ operator is pretty common, though, and probably worth using.

Check your Learning

To check your answers, open ts-node in your command line and copy these commands.

At the end of the code block below, what will be printed?

let a = 7;
let b = 3;
a = a - b;
a = a**2;
a++;
b++;
console.log(a+b);

Will the following statement be true or false?

! ((2 == 2) || (3 != 3))

What would be the value of b below?

let s = "23";
let n = 43
let b = s + n;